In rotating well pumping apparatus, it is customary to employ a stuffing box at the wellhead to prevent oil, water, and gases produced under pressure by the rotating pumping apparatus from escaping into the atmosphere.
Generally, the stuffing box surrounds a portion of the polished rod in order to guide or center the polished rod for rotary movement without the escape of produced liquids or gases. Typically, the stuffing box is able to prevent the loss of produced liquids or gases by utilization of a series of annular packing elements which are compressed until they engage the external surface of the polished rod. The stuffing box is connected directly into the well production string, by threading the lower end of the stuffing box assembly into a conventional flow tee or pipe fitting.
A problem experienced with stuffing boxes for rotary applications is excessive packing wear which results in leakage. For example, in rotary drive downhole progressive cavity pumps, the pump barrel and pump screw are installed in the well. The pump barrel is attached to the bottom of the production piping or tubing and can be installed as deep as 1500 feet or more. The screw or rotor which rotates inside the stationary barrel squeezes the fluid up through the pump and tubing and is attached to a shaft which extends from the screw to the rotary drive assembly at the surface. Typically, surface-mounted rotary drive assemblies have used conventional style wellhead stuffing boxes. The stuffing box has included a brass bushing placed in the upper and lower stuffing box cavity with packing rings installed between the two bushings. Using conventional brass bushings and packing can cause severe wear on the drive rod, stationary brass bushing and the packing. This in turn causes packing wear and polished rod wear resulting in excess leaked production lost to the environment.